I got the same problem with OZ 4.9 version, when adding water, sometimes, under the water, mesh structure was fucked up, with distorted textures, big holes, but OZ 5.0 fixed it, well, ad least it fixed it for me.
Maybe WC made some change lately in a version he sended me, he is taking a break atm, and if you are still having those problems with OZ 5.0, give me your mail and i will send you latest OZ version WC sended me, hoping that would solve the problem.
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